1. Field of the Invention
The invention relates to solenoid valves and more particularly to such a solenoid valve including a check valve in a housing so that gas may flow to air chambers and spaces respectively without lubrication oil and water accumulation, and the valve can be opened or closed manually in response to insufficient gas or power off.
2. Description of Related Art
A conventional solenoid valve shown in FIGS. 11 and 12 is characterized in the following. In a fail-safe mode a pilot solenoid valve 53 is electrically powered to open a port 531. Next, a compressed air source 5 supplies compressed air to the pilot solenoid valve 53 via a path 513, a switch 55, and compress a spool 5100 accordingly. The compressed air source 5 further supplies compressed air to an air chamber 611 of a pneumatic cylinder 6 via a first port 515 and an independent check valve 612 attached to the cylinder 6. Further, air in the air chamber 611 flows to a hole element 510 in a body 51 via a 1B port 64 and an air inlet 512. Furthermore, air flows to a first space 67 in the pneumatic cylinder 6 via a second port 516 and a 1C port 65. And in turn, two pistons 62 are pushed toward two adjacent second spaces 68 respectively. As such, a pinion 69 in the pneumatic cylinder 6 rotates counterclockwise to open the valve.
Compressed lubricated air may flow to the pneumatic cylinder 6 via the air chamber 611 first before the air flow to the first space 67 and the second space 68 and due to the density, the lubricated oil and moisture may accumulate in the air chamber 611 which result the insufficient lubrication to both the first space 67 and the second space 68 and make the space of the air chamber 611 decreased. In the event of air failure, insufficient air volume may be supplied from the air chamber 611. As a result, operation may be malfunctioned. Thus, the need for improvement still exists.